Doctor blade for photogravure printing machine

ABSTRACT

A doctor blade assembly for photogravure printing machines for the removal of excess printing ink from a printing surface comprising an elongated doctor blade having opposite longitudinal edge portions one of which has a contact surface adapted to contact a printing surface, a strengthening element secured to said doctor blade therealong and having a longitudinal edge terminating short of the contact surface, a plurality of individually connected though sequentially removable means between the longitudinal edge and the contact surface for supportive back-up of said one edge portion and for sequentially reducing the length of the removable means in a direction away from the contact surface whereby the distance between the last of the removable means and the contact surface is maintained essentially constant during the progressive wear of the doctor blade one edge portion.

A Unite States Patent [191 D'atwyler DOCTOR BLADE FOR PHOTOGRAVUREPRINTING MACHINE Max Diitwyler, Bleienbach, Switzerland [75] inventor:

[73] Assignee: Max Datwyler & Co., Bleienbach,

Switzerland [22] Filed: Sept. 17, 1973 [21] Appl. No.: 397,877

[30] Foreign Application Priority Data [451 May 20, 1975 PrimaryExaminerStephen C. Pellegrino Attorney, Agent, or FirmDiller, Brown,Ramik & Wight [57] ABSTRACT A doctor blade assembly for photogravureprinting machines for the removal of excess printing ink from a printingsurface comprising an elongated doctor blade having oppositelongitudinal edge portions one of which has a contact surface adapted tocontact a printing surface, a strengthening element secured to saiddoctor blade therealong and having a longitudinal edge terminating shortof the contact surface, a plurality of individually connected thoughsequentially removable means between the longitudinal edge and thecontact surface for supportive back-up of said one edge portion and forsequentially reducing the length of the removable means in a directionaway from the contact surface whereby the distance between the last ofthe removable means and the contact surface is maintained essentiallyconstant during the progressive wear of the doctor blade one edgeportion.

14 Claims, 5 Drawing Figures PATENTEU M20197?) 3,884,145

SHEET 3 BF 3 Fig.5

DOCTOR BLADE FOR PI-IOTOGRAVURE PRINTING MACHINE BACKGROUND OF THEINVENTION The present invention relates to a new and improvedconstruction of a doctor blade assembly for photogravure printingmachines for the removal of printing ink or the like from a printingsurface, in particular from a printing cylinder.

It is well known in this particular field that the surface of the doctorblade contacting the printing cylinder of the photogravure printingmachine is subject to material wear. Due to this material wearphenomenon this contact surface of the prior art doctor blades whichbear against the printing cylinder, and wherein the end confronting theprinting cylinder is constructed to possess a substantially wedge-shapedcross-section, always becomes wider. This in turn impairs the wipingaction of the doctor blade and leads to undesired fluctuations in thecolor tone of the printed product. The Contact surface of the doctorblade is also referred to as the doctor blade bevel.

In order to prevent the above-discussed undesirable effects the doctorblade must be frequently replaced and reground, each time requiringstandstill of the printing machine.

SUMMARY OF THE INVENTION Hence, it is a primary object of the presentinvention to provide an improved construction of a doctor blade assemblyfor photogravure printing machines or the like which is not associatedwith the aforementioned drawbacks and limitations of the prior artproposals.

Another and more specific object of the present invention relates to anew and improved construction of a doctor blade assembly which overcomesthe aforementioned drawbacks and wherein wear of the doctor blade bevelcontacting the printing surface does not produce any impairment in theink wiping action of the doctor blade.

Now in order to implement these and still further objects of theinvention, which will become more readily apparent as the descriptionproceeds, the doctor blade assembly of the previously mentioned type ismanifested by the features that there is provided a doctor blade whichhas a contact surface which contacts the printing surface and thisdoctor blade is connected with a strengthening element. Thestrengthening element terminates at a spacing from the contact surfaceof the doctor blade, and at the end of such support element whichconfronts the contact surface is provided a number of individualsections. These individual sections are connected with one another andare individually removable so that by removing individual sections thespacing or distance between the contact surface of the doctor blade andthe last of the individual sections is maintained essentially constantduring the progressive wear of the contact surface.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be betterunderstood and objects other than those set forth above, will becomeapparent when consideration is given to the following detaileddescription thereof. Such description makes reference to the annexeddrawings wherein:

FIG. 1 is a schematic sectional view of a first exemplary embodiment ofa doctor blade assembly for photogravure printing machines and designedaccording to the teachings of the present invention;

FIG. 2 is a second embodiment of a doctor blade assembly;

FIG. 3 is a third embodiment of a doctor blade assembly;

FIG. 4 is a fourth embodiment of a doctor blade assembly; and

FIG. 5 is a fifth embodiment of a doctor blade assembly designedaccording to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Describing now thedrawings it is to be understood that in each of the exemplaryillustrated embodiments of doctor blade assemblies constructed accordingto the teachings of the invention there have only been convenientlyshown in the drawings those portions of the doctor blade assemblieswhich are significant for understanding the basic concepts of theinvention and which generally confront the schematically portrayedprinting cylinder Z of a rotary photogravure printing machine. Tosimplify the drawing illustration the end of the doctor blade assemblywhich is clamped in standard fashion at a doctor blade holder has beenomitted.

Now each of the constructions of doctor blade assemblies depicted inFIGS. 1 to 5 will be understood to incorporate a substantiallyplate-shaped doctor blade 1. This doctor blade 1 extends over the entirewidth of the doctor blade assembly and is delimited or bounded by twoboundary surfaces 2 and 3 which are essentially parallel to one another.The doctor blade 1 possesses a contact surface 4 which extends at aninclination with respect to the surfaces 2 and 3, as shown, and alsobears against the printing cylinder Z. As mentioned heretofore, thiscontact surface 4 of the doctor blade is also sometimes referred to inthe art as the doctor blade bevel. Since the spacing between bothsurfaces 2 and 3 remains constant the width of the doctor blade bevel 4essentially remains constant during wear of the scraper element 1.

Since the width of the doctor blade bevel 4 should not exceed a certainor predetermined value, which for instance is in the order of magnitudeof about 50 pm, in order to obtain at any time a sufficientlysatisfactory wiping of the ink from the surface of the printingcylinder, the doctor blade 1 must be constructed correspondingly thin.In order to impart to such thin doctor blade 1 a sufficient bendingstrength it is connected with a strengthening element 5.

With the exemplary embodiment of doctor blade assembly depicted in FIG.1 this strengthening element 5 embodies a strengthening member 6 securedat the surface 2 of the doctor blade 1, and at one end 6a of suchstrengthening member 6 there are means in the form of a number ofindividual abutting sections 7. These sections 7 are connected at theirjoint surfaces with one another, as will be explained more fullyhereinafter, for instance by adhesively bonding the same, and with thedoctor blade 1 in such a way that in each instance individual sectionscan be detached from the neighboring sections. The end 8 of the lastsection which bears against the doctor blade 1 extends at a spacing froma longitudinal edge 9 of the contact surface 4 of the doctor blade 1 andwhich edge 9 bears against the printing cylinder Z. The section 7thereby collectively define a plurality of individually connected thoughsequentially removable means 7 between a longitudinal edge or end(unnumbered) of the strengthening element 6 and the contact surface 4 oredge 9 of the doctor blade 1 for supportive back-up thereof and forsequentially reducing the length of the removable means 7 in a directionaway from the contact surface 4 whereby the distance between the last ofthe removable means 7 and the contact surface 4 is maintainedessentially constant during the progressive wear of the doctor blade 1.

The doctor blade I and the strengthening element prior to attachment areadjusted with regard to their mutual position by means of a centeringtool inserted into the bores 10 and 10a of such components.

Now if the doctor blade 1 is worn down during use, then in each case byremoving the forwardmost section 70 it is possible to essentiallymaintain constant the spacing between the edges 8 and 9. In this waythere is achieved the result that the portion la of the doctor blade 1which protrudes past the strengthening element 5 always remainsapproximately the same size, which apart from the constant width of thedoctor blade bevel 4 leads to a constant wiping action of the doctorblade, so that there can be effectively avoided fluctuations in thecolor at the printed products.

Since the sections 7 can be detached or removed during rotation of theprinting cylinder Z, there is not required any downtime or standstill ofthe printing machine for compensating the wear of the doctor blade.

The exemplary embodiments of doctor blades depicted in FIGS. 2 to 5respectively, essentially correspond to the exemplary embodiment ofdoctor blade assembly above in connection with FIG. 1 and only deviatetherefrom in the construction of the sections 7.

Now with the exemplary embodiments depicted in FIGS. 2 and 3 thesections 7 possess extended portions or extensions 11 which bear insuperimposed fashion upon the strengthening member 6. These extensionsor extended portions 11 are detachably connected with one another andthe lowermost extension or extended portion 11 is additionally connectedwith the strengthening member 6.

In the exemplary embodiment of FIG. 2 the mutually abutting sections 7are connected with one another at their abutting or joint surfaces,whereas with the exemplary embodiment of FIG. 3 the sections 7 arearranged at a spacing from one another in the direction of the doctorblade bevel 4. In this case the connection of these sections 7 occurssolely via the abutting and detachable interconnected extension orextended portions 11 of such sections 7. Apart from the possibility ofremoving or detaching the individual sections 7 manually in eachinstance, there are also other detachment techniques which can beconceivably employed, for instance based upon mechanical, chemical orelectrical principles. Such techniques also can be combined with asuitable measuring device which measures the length of the portion la ofthe doctor blade 1 which protrudes past the support element 5 and as afunction of the wear of the doctor blade end automatically brings aboutremoval or detachment of a section 7.

For the doctor blade 1, the strengthening member 6, the sections 7 andthe extensions or extended portions 11 there are employed suitablematerials for the relevant doctor blade constructions.

Thus, for instance for the doctor blade there is preferably used ametallic material, whereas the remaining components 6, 7 and 11 forinstance are formed of plastic or a metallic material.

For the connection of the sections 7 and the extensions 11 with oneanother and with the strengthening member 6 and the doctor blade 1 thereare to be chosen connection means which, on the one hand, ensure for apermanent connection in order to avoid any undesired detachment of theindividual sections 7 and the connection or extended portions 11, and onthe other hand, when required, still permit of an effortless detachmentof such components. All of these requirements can be fulfilled byconnection means for instance in the form of suitable commerciallyavailable adhesives; furthermore, connections of the desired type alsocan be obtained by means of suitable weldingand soldering procedures, asschematically indicated by reference character 20 for instance in FIG.1.

While there is shown and described present preferred embodiments of theinvention, it is to be distinctly understood that the invention is notlimited thereto, but may be otherwise variously embodied and practicedwithin the scope of the following claims. Accordingly,

What is claimed is:

l. A doctor blade assembly for photogravure printing machines for theremoval of excess printing ink from a printing surface comprising anelongated doctor blade having opposite longitudinal edge portions one ofwhich has a contact surface adapted to contact a printing surface, astrengthening element secured to said doctor blade therealong and havinga longitudinal edge terminating short of said contact surface, aplurality of individually connected though sequentially removable meansbetween said longitudinal edge and said contact surface for supportiveback-up of said one edge portion and for sequentially reducing thelength of said removable means in a direction away from said contactsurface whereby the distance between the last of said removable meansand said contact surface is maintained essentially constant during theprogressive wear of said doctor blade one edge portion.

2. The doctor blade assembly as defined in claim 1 wherein saidremovable means extend longitudinally along the length of said doctorblade.

3. The doctor blade assembly as defined in claim 1 wherein saidremovable means are a plurality of elongated sections extendinglongitudinally along the length of said doctor blade.

4. The doctor blade assembly as defined in claim 3 wherein said sectionsare connected with one another by an adhesive.

5. The doctor blade assembly as defined in claim 3 wherein said sectionsare connected with one another by welding.

6. The doctor blade assembly as defined in claim 3 wherein said sectionsare connected with one another by soldering.

7. The doctor blade assembly as defined in claim 3 wherein saidelongated sections are disposed in shinglelike fashion upon said doctorblade.

8. The doctor blade assembly as defined in claim 3 wherein eachelongated section has a first longitudinal edge generally parallel tosaid doctor blade and a second longitudinal edge directed at adownwardly directed incline in a direction toward said contact surface.

9. The doctor blade assembly as defined in claim 3 wherein eachelongated section has a first longitudinal edge generally parallel tosaid doctor blade, a second longitudinal edge directed at a downwardlydirected incline in a direction toward said contact surface, and saidsecond longitudinal edges are in spaced relationship to each other.

10. The doctor blade assembly as defined in claim 3 wherein eachelongated section has a first longitudinal edge generally parallel tosaid doctor blade, a second longitudinal edge directed at a downwardlydirected incline in a direction toward said contact surface, and saidsecond longitudinal edges are in spaced parallel relationship to eachother.

11. The doctor blade assembly as defined in claim 7 wherein eachelongated section has an edge resting

1. A doctor blade assembly for photogravure printing machines for theremoval of excess printing ink from a printing surface comprising anelongated doctor blade having opposite longitudinal edge portions one ofwhich has a contact surface adapted to contact a printing surface, astrengthening element secured to said doctor blade therealong and havinga longitudinal edge terminating short of said contact surface, aplurality of individually connected though sequentially removable meansbetween said longitudinal edge and said contact surface for supportiveback-up of said one edge portion and for sequentially reducing thelength of said removable means in a direction away from said contactsurface whereby the distance between the last of said removable meansand said contact surface is maintained essentially constant during theprogressive wear of said doctor blade one edge portion.
 2. The doctorblade assembly as defined in claim 1 wherein said removable means extendlongitudinally along the length of said doctor blade.
 3. The doctorblade assembly as defined in claim 1 wherein said removable means are aplurality of elongated sections extending longitudinally along thelength of said doctor blade.
 4. The doctor blade assembly as defined inclaim 3 wherein said sections are connected with one another by anadhesive.
 5. The doctor blade assembly as defined in claim 3 whereinsaid sections are connected with one another by welding.
 6. The doctorblade assembly as defined in claim 3 wherein said sections are connectedwith one another by soldering.
 7. The doctor blade assembly as definedin claim 3 wherein said elongated sections are disposed in shingle-likefashion upon said doctor blade.
 8. The doctor blade assembly as definedin claim 3 wherein each elongated section has a first longitudinal edgegenerally parallel to said doctor blade and a second longitudinal edgedirected at a downwardly directed incline in a direction toward saidcontact surface.
 9. The doctor blade assembly as defined in claim 3wherein each elongated section has a first longitudinal edge generallyparallel to said doctor blade, a second longitudinal edge directed at adownwardly directed incline in a direction toward said contact surface,and said second longitudinal edges are in spaced relationship to eachother.
 10. The doctor blade assembly as defined in claim 3 wherein eachelongated section has a first longitudinal edge generally parallel tosaid doctor blade, a second longitudinal edge directed at a downwardlydirected incline in a direction toward said contact surface, and saidsecond longitudinal edges are in spaced parallel relationship to eachother.
 11. The doctor blade assembly as defined in claim 7 wherein eachelongated section has an edge resting upon said doctor blade.
 12. Thedoctor blade assembly as defined in claim 8 wherein each secondlongitudinal edge of each elongated section has an edge resting uponsaid doctor blade.
 13. The doctor blade assembly as defined in claim 9wherein each second longitudinal edge of each elongated section has anedge resting upon said doctor blade.
 14. The doctor blade assembly asdefined in claim 10 wherein each second longitudinal edge of eachelongated section has an edge resting upon said doctor blade.